1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus capable of synthesizing plural images.
2. Related Background Art
There are already known image synthesizing apparatus for preparing an image by synthesizing plural images.
Among such apparatus, there is for example known one, disclosed in U.S. Pat. No. 4,320,962 of the present assignee, for storing two original images in two memories and synthesizing said two images by displacing the timing of image signal reading from said two memories. There have also been various proposals on image synthesis, such as those disclosed in U.S. Pat. No. 4,417,805 and U.S. patent application Ser. No. 06/932,030.
However, such apparatus are only capable of reading and synthesizing original images, and are unable to effect synthesis with images other than such original image.
There is also known a digital copying machine capable of trimming a predetermined portion of an original image, for example with a digitizer, and copying the image only of the thus-trimmed image.
However, in synthesizing a video signal supplied from the outside in such copying machine, there is required a complex structure for designating the synthesizing position of said video signal, separately from the trimming function of said copying machine.
Also, there is already known a recording apparatus having a page memory capable of storing input image data of at least a frame, and capable of producing plural prints of the same image based on image data read from said page memory.
In such apparatus there may occur jamming of printing sheets or exhaustion of the supply of printing sheets in the course of printing plural sheets.
In order to rectify such situation, the present applicant has already proposed a technique involving not repeating the data writing into the page memory but automatically continuing the printing of plural sheets after such error state is resolved.
However, such apparatus is often inconvenient for use, since the printing of plural sheets is automatically continued when the error state is resolved.
More specifically, when the operator resolves the error state, the printing operation is executed immediately without any other actuation. Such situation is different from the ordinary printing operation and may be misunderstood as an error operation by the operator.
Furthermore, if the aforementioned page memory is composed of a memory device requiring refreshing at a predetermined interval, such as a DRAM, synchronization signals for said refreshing operation are obtained for example from a clock generator to retain the internally stored information.
However, if the reference signals generated for refreshing operation of the DRAM are switched to other non-synchronized signals for some reason, the refreshing interval may be prolonged before or after said switching, whereby the stored information may become unstable and eventually lost.